Statistics of D. hyalina. 



467 



2 in the 12-15 m. level, and one in the 15-18 m. level. In these 

 deeper levels, however, a larger per cent, of the total number 

 of Daphnia was obtained than was the case with the more nu- 

 merous Diaptomus and Cyclops. 



Diurnal distribution. — Very little need be said on this sub- 

 ject beyond a reference to the tables. In the first three periods 

 the actual number obtained at night was larger than that caught 

 by day. In Period III especially, the numbers differ consider- 

 ably, being 210 by day as an average and 329 by night. The 

 numbers are, however, so small that chance has probably de- 

 termined this distribution. In the percentile distribution little 

 difference appears between day and night. In Period I there is 

 a slight excess in the 0-3 level at night. In all other periods 

 the upper level is smaller at night than during the day. 

 There is no positive indication of either ascent or descent of 

 this species. 



The center of distribution ranged from 3. 5 m. below the sur- 

 face in Period IV to 4.5 m. in Period I. It averaged about 4.1 m. 

 for the month. 



STATISTICS Of D. HYALINA. 



Table N — Vertical distribution day and night. Average of month. 



Depth. 



Obs 



Average. 



Obs. 



33 

 31 

 32 

 30 

 31 

 27 



Day. 



Obs. 



Night. 



Meters. 



No. 



Per cent. 



No. 



88 



61 



41 



9 



1 







Per cent. 



44 

 30.5 

 20 5 

 4.5. 

 .5 



No. 



103 



73 



53 



20 



3 



1 



Per ceDt. 



0—3 



59 

 57 

 58 

 56 

 54 

 50 



94 



66 



46 



13 



2 



1 



222 



42 34 



29.72 



20.72 



5.85 



.90 



.45 



26 

 26 

 26 

 23 

 24 

 23 



40.7 



3—6 



28.8 



6-9 



9-12 



12—15 



15—18 



20.9 

 7.9 

 1.18 

 .39 







Total 









200 







253 











The facts of this table are represented in PI. X, fig. 3. 

 31 



